Semivolatile and volatile compounds from the pyrolysis and combustion of polyvinyl chloride

摘要

Emissions evolved from the pyrolysis and combustion of polyvinyl chloride (PVC) were studied at four different temperatures (500, 700,850 and 1000 °C) in a horizontal laboratory tubular quartz reactor in order to analyse the influence of both temperature and reactionatmosphere on the final products from thermal and oxidative reactions. It was observed that the CO2/CO ratio increased with temperature.Methane was the only light hydrocarbon whose yield increased with temperature up to 1000 °C. Benzene was rather stable at hightemperatures, but in general, combustion at temperatures above 500 °C was enough to destroy light hydrocarbons. Semivolatile hydrocarbonswere collected in XAD-2 resin and more than 160 compounds were detected. Trends on polyaromatic hydrocarbon (PAH) yields showed thatmost had a maximum at 850 °C in pyrolysis, but naphthalene at 700 °C. Formation of chlorinated aromatics was detected. A detailed analysisof all isomers of chlorobenzenes and chlorophenols was performed. Both of them reached higher total yields in combustion runs, the first oneshaving a maximum at 700 °C and the latter at 500 °C. Pyrolysis and combustion runs at 850 °C were conducted to study the formation ofpolychlorodibenzo- p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs). There was more than 20-fold increase in total yields frompyrolysis to combustion, and PCDF yields represented in each case about 10 times PCDD yields.